CN1568339A

CN1568339A - Poly (trimethylene terephthalate) pellets and method for production thereof

Info

Publication number: CN1568339A
Application number: CNA028199685A
Authority: CN
Inventors: 冈岛真一; 加藤仁一郎; 藤本克宏
Original assignee: Asahi Chemical Industry Co Ltd
Current assignee: Asahi Kasei Corp
Priority date: 2001-10-11
Filing date: 2002-04-26
Publication date: 2005-01-19
Anticipated expiration: 2022-04-26
Also published as: JP3970245B2; MXPA04003205A; DE60220692D1; ATE364650T1; EP1435367B1; KR20040052229A; WO2003033564A1; EP1435367A1; EP1435367A4; US6916535B2; TWI294436B; ES2284857T3; US20030092874A1; KR100544250B1; JPWO2003033564A1; DE60220692T2; CN1252123C

Abstract

Pellets of polytrimethylene terephthalate in which 80 wt.% or more of the repeating units are accounted for by trimethylene terephthalate units, bis(3-hydroxypropyl) ether has been copolymerized in a proportion of 0.01 to 2 wt.%, the content of terminal carboxyl groups is 25 meq/kg or lower, and the intrinsic viscosity is 0.8 to 2 dl/g, characterized in that the pellets have a value of L* of 75 or higher and a value of b* of -2 to 5 and weigh 1 to 50 mg per pellet.

Description

Polytrimethylene terephthalate pellets and process for producing the same

Technical Field

The present invention relates to pellets (ペレツト) of polytrimethylene terephthalate and a process for producing the same.

Background

Polytrimethylene terephthalate fibers (hereinafter, polytrimethylene terephthalate is abbreviated as PTT) have surprisingly excellent properties such as soft hand, drapability (ドレ - プ property), stretchability, low-temperature dyeability, weather resistance, and the like, and have various excellent properties not possessed by conventional synthetic fibers such as polyethylene terephthalate (hereinafter, polyethylene terephthalate is abbreviated as PET) and nylon 6 fibers.

The present applicant has overcome various difficulties associated with polymerization, spinning, processing of PTT fibers, development of commercial products, etc. of PTT, and has recently introduced PTT fibers into the market for the first time in the world (trademark: "ソロ (Solo)" fibers).

PTT is obtained by polycondensation of terephthalic acid or a lower alcohol ester of terephthalic acid with 1, 3-propanediol (also referred to as propylene glycol, hereinafter 1, 3-propanediol is abbreviated as PDO).

The elementary reaction constituting the polycondensation reaction of PTT is mainly composed of the following two reactions. The positive reaction is a chain extension reaction by depdo of two terminal hydroxyl groups (see the following formula (a)). The side reactions are a reaction in which the ester portion is decomposed by the PDO that is not discharged (i.e., a reverse reaction of formula (a)) and a thermal decomposition reaction of the ester portion (see the following formula (b)). In the following formula (a), k1 is a reaction rate constant of the reaction in the rightward direction, and k2 is a reaction rate constant of the reaction in the leftward direction. In the following formula (b), kd is a reaction rate constant of the reaction in the rightward direction.

Since PTT is more likely to undergo a thermal decomposition reaction (in other words, kd is large) than PET or polybutylene terephthalate (hereinafter abbreviated as PBT) having a similar skeleton, it is difficult to increase the molecular weight by melt polymerization alone. Therefore, to produce a high molecular weight PTT, it is generally carried out that: a method of producing a high molecular weight by first producing a low molecular weight prepolymer by melt polymerization, cooling and solidifying the obtained prepolymer once, and then conducting polycondensation at a temperature not higher than the melting point of the prepolymer, i.e., a method of producing a high molecular weight by using both melt polymerization and solid phase polymerization.

However, in the melt polymerization or solid-phase polymerization of PTT, there are various problems caused by the characteristic polymer properties of PTT.

The first problem is that PTT is liable to be thermally decomposed in the melting stage. In the PTT, since kd of the above formula (b) is large, a viscosity decrease tends to occur in a molten state. The molecular terminal carboxyl group and the molecular terminal allyl group generated by the thermal decomposition in the molten state further promote the thermal decomposition, which causes a decrease in the whiteness and oxidation resistance of the PTT. Therefore, it is a necessary condition to obtain a high-quality PTT by suppressing the thermal decomposition as much as possible in the production stage of the PTT. However, in the known art, the problem is not sufficiently solved.

The second problem is that the PTT pellets are easily broken and become powdery. For example, in the stages of solid-phase polymerization, drying, transportation, etc., the pellets rub against each other, but in this case, the pellets are relatively easily broken and become powder. In particular, in the solid-phase polymerization stage, when the PTT pellets are broken and become powder, various problems such as yarn breakage, fuzzing, white spots (フイツシユアイ) and the like occur in the melt-molding stage of spinning, film formation, molding and the like.

That is, since the powdery PTT has a large surface area, when solid-phase polymerization is carried out by mixing it in pellets, the discharge of PDO in the above formula (a) proceeds excessively efficiently, and therefore the molecular weight becomes higher than that of the pellet-shaped PTT, and the melt viscosity becomes abnormally high. Therefore, if a PTT obtained by solid-phase polymerization is used in the melt-molding step, the powder having a high molecular weight is not completely melted in the melt-molding step, so that the molten state of the polymer becomes non-uniform, which causes yarn breakage or fuzzing in the spinning process. Further, the powdery material adheres to the inner wall of the solid phase polymerization apparatus and stays for a long period of time, causing thermal degradation or coloration, and if it is discharged accidentally, it becomes a cause of lowering the color tone or oxidation resistance stability of the molten molded product. In order to avoid such a problem, a method of removing the broken product or the powder before melt molding is considered, but since a removal step is necessary, if the amount of the broken product or the powder is large, a large amount of raw material is lost, and the production cost is increased.

The two problems described above are hardly a problem for PET and PBT having similar chemical structures. These polymers have a much smaller thermal decomposition rate constant than PTT, corresponding to kd, and even if the pellets rub against each other, the degree of powder generation is much smaller. That is, the above-mentioned problems are unique to PTT, and it is extremely difficult to assume a solution to these problems from the descriptions of publicly known documents relating to PET and PBT. Further, there is no description or suggestion of means for solving these problems even in the publicly known documents relating to the polymerization of PTT.

For example, Japanese patent application laid-open No. 2000-159875 proposes a method for obtaining a high-quality PTT by solid-phase polymerization of a polymer having a low content of terminal vinyl groups by melt polycondensation under reduced pressure or in an inert atmosphere using a mixed catalyst of Ti and Mg in a specific state. However, in this method, since Mg is used as a catalyst, grayish shade, L, appears in the hue^*The value is reduced to about 60 to 70, and the color difference is small. Further, the problem of the generation of the powder is not recognized, and it is not suggested how to solve the problem.

WO97/23543 describes a method of producing a solid PTT having an apparent crystallite size of not less than 18nm by dropping a molten PTT having a low polymerization degree onto a hot plate without forming it into pellets, crystallizing the molten PTT at 60 to 190 ℃ and then carrying out solid-phase polymerization. However, the surface of the PTT obtained by this method is extremely uneven, and powder is easily generated when the PTTis rubbed against each other. In addition, this specification does not describe any technique for improving color tone and oxidation resistance stability.

In U.S. Pat. No. 2001/0056172-A1, a process for solid phase polymerization of PTT pellets is described. However, only a technique of applying a solid phase polymerization technique of general PET or the like to PTT is disclosed, and the problems of whiteness, oxidation resistance, generation of powder, and the like peculiar to PTT are not recognized, and a solution thereof is not described at all.

WO98/23662, which is incorporated herein by reference, describes a method in which an end-capped PTT is pelletized with a hindered phenol-based stabilizer and then subjected to solid-phase polymerization. In addition, in example 8 of the specification of WO99/11709, a method is described in which a PTT containing a phosphorus-based stabilizer is pelletized and then subjected to solid-phase polymerization. However, the oxidation resistance stability and the generation of powder are not recognized, and no solution is described.

Disclosure of the invention

The present invention addresses the problem of providing PTT pellets which are less likely to crack or generate a powdery material and which are excellent in whiteness and oxidation resistance. Further, there are provided PTT prepolymer pellets which are less likely to break or generate a powdery material during solid-phase polymerization and which are less likely to be colored and which can give high-quality PTT pellets, and a process for producing the same.

As a result of intensive studies on the melt polymerization and solid-phase polymerization of PTT to solve the above problems, the present inventors have found that the above problems can be solved by solid-phase polymerizing pellets of a PTT prepolymer having a small particle diameter and a small degree of thermal decomposition preferably under conditions such that water, PDO, or the like as a polymerization by-product is efficiently discharged, and have completed the present invention.

Namely, the present invention relates to the following.

1. A PTT pellet satisfying the following (1) to (7):

(1) PTT is a polymer in which not less than 80% by weight of the repeating units are composed of trimethylene terephthalate units,

(2) PTT is copolymerized with bis (3-hydroxypropyl) ether at a copolymerization ratio of 0.01 to 2% by weight,

(3) the amount of the terminal carboxyl group of PTT is not more than 25 meq/kg,

(4) the intrinsic viscosity of the PTT is 0.8 to 2dl/g,

(5) l of the pellet^*Is not less than 75 percent of the total weight of the composition,

(6) b of the pellet^*The amount of the organic solvent is-2 to 5,

(7) the mass of each pellet is 1-50 mg/pellet.

2. The PTT pellets as described in the above 1, wherein the content of the trimethylene terephthalate cyclic dimer is not more than 1.5% by weight.

3. The PTT pellet as described in 1 or 2 above, wherein the specific surface area of each pellet is 10 to 50cm²/g。

4. The PTT pellet as described in 1 above, characterized in that the degree of crystallinity is 40 to 60%.

5. The PTT pellet as described in 1 above, wherein the Vickers hardness is 10 to 30kg/mm²。

6. A process for producing PTT pellets, characterized by subjecting pellets of a PTTprepolymer satisfying the following (1) to (7) to solid-phase polymerization:

(1) the PTT prepolymer is a PTT prepolymer in which not less than 80% by weight of the repeating units are composed of trimethylene terephthalate units,

(2) the PTT prepolymer is copolymerized with bis (3-hydroxypropyl) ether, the copolymerization ratio of the PTT prepolymer is 0.01-2 wt%,

(3) the amount of the terminal carboxyl group of the PTT prepolymer is not more than 35 meq/kg,

(4) the intrinsic viscosity of the PTT prepolymer is 0.1 to 1dl/g,

(5) l of prepolymer pellets^*Is not less than 75 percent of the total weight of the composition,

(6) b of prepolymer pellets^*The amount of the organic acid is-3 to 6,

(7) the mass of each prepolymer pellet is 1-50 mg/pellet.

7. The process for producing PTT pellets as described in the above 6, wherein the solid-phase polymerization is carried out in an inert gas stream under the conditions of the following (1) and (2),

(1) the solid-phase polymerization temperature is 190-220 ℃,

(2) the superficial velocity of the inert gas is not less than 10 cm/min.

8. The process for producing PTT pellets as described in the above 6, wherein the solid-phase polymerization is carried out under reduced pressure under the conditions of the following (1) and (2),

(1) the solid-phase polymerization temperature is 190-220 ℃,

(2) the degree of vacuum was not higher than 30 kPa.

9. The method for producing PTT pellets according to any one of claims 6 to 8, wherein the solid-phase polymerization is carried out after heat treatment is carried out in advance to a crystallinity of 20 to 60% before the solid-phase polymerization.

10. The method for producing PTT pellets according to any one of claims 6 to 9, wherein the solid-phase polymerization is continuous solid-phase polymerization or batch solid-phase polymerization.

11. A melt-molded article using the PTT pellet as described in any one of 1 to 5 above.

The present invention will be described in detail below.

The pellets of the present invention are composed of PTT. The pellet is a substance which is easily melt-molded and solidifies the polymer into a granular form, and is also called a chip (チツプ).

In the present invention, not less than 80% by weight of the repeating units in the PTT are composed of trimethylene terephthalate units. Comonomers other than terephthalic acid and PDO may be copolymerized in the range of not more than 20% by weight, preferably not more than 10% by weight of the repeating unit.

Examples of the comonomer include oxalic acid, succinic acid, adipic acid, sebacic acid, dodecanoic acid, dodecanedioic acid, cyclohexanedicarboxylic acid, ethylene glycol, butanediol, hexanediol, cyclohexanediol, cyclohexanedimethanol, a propylene glycol dimer, and a polyalkylene glycol having an average molecular weight of 400 to 20000, and these may be used alone or in combination of 2 or more. In addition, as a comonomer, sulfonate can be copolymerized, but in melt polymerization, polymerization is difficult, and the yarn strength is low, so it is not preferable.

The PTT pellets of the present invention may be co-polycondensed or mixed with various additives, for example, a delustering agent, a heat stabilizer, an antifoaming agent, a positive coloring agent, a flame retardant,an antioxidant, an ultraviolet absorber, an infrared absorber, a crystal nucleating agent, a fluorescent brightener, etc., as required. The matting agent is preferably titanium oxide, and the content thereof is preferably 0.01 to 3% by weight relative to the pellets from the viewpoints of reducing the generation of cracks or powder and reducing the friction during molding. Further, in order to suppress thermal decomposition during the polymerization, a thermal stabilizer is preferably used, and particularly, a phosphorus compound such as phosphoric acid, trimethyl phosphate, triethyl phosphate or the like is preferably contained in an amount of 2 to 250ppm, preferably 10 to 100ppm of the phosphorus element with respect to the pellets. For the same purpose, the hindered phenol antioxidant may be used in an amount of 0.01 to 1 wt% relative to the pellet. In addition, for preventing coloration, it is preferable to add a color tone adjusting agent such as cobalt acetate, cobalt formate, or a fluorescent whitening agent in an amount of 0.0001 to 0.05 wt% relative to the beads.

The PTT pellet of the invention is as follows: the intrinsic viscosity of the PTT is 0.8 to 2dl/g, preferably 0.8 to 1.5 dl/g. When the intrinsic viscosity is within this range, breakage of the pellets or generation of a powdery material is reduced, and a molded article having excellent strength and durability can be obtained.

L of the PTT pellets of the present invention^*A value of not less than 75, preferably not less than 80, more preferably not less than 85, and in addition, b^*The value is-2 to 5, preferably-1 to 5, more preferably-1 to 4. L is^*Value b and^*the value is expressed by CIE-L^*a^*b^*(CIE1976) index of color tone expressed by the color system. L is^*Indicating the brightness, the larger the value the brighter. b^*The values represent the yellowness (yellowness 12415s), the greater the number the stronger the yellowness. L is^*Value b and^*when the value is within the above range, for example, when coloring is carried out using a dye or a pigment, a product having excellent color development and vividness can be obtained.

The mass of each PTT pellet is 1-50 mg/pellet. If the amount is within this range, the pellets are less likely to break, and the feeding ability into the screw of the extruder is good, and the surrounding gas is less likely to be entrapped (entrapped き Write み) in the extruder using a single screw used in ordinary melt spinning, so that yarn breakage and fuzz are not generated. In order to suppress the breakage of pellets or the generation of powder, the solid phase polymerization is carried out at a low temperature in a short time, and the mass of the pellets is preferably 1 to 30 mg/piece, more preferably 1 to 25 mg/piece.

The specific surface area of each small ball is preferably 10-50 cm²A concentration of 20 to 50cm²(ii) in terms of/g. When the amount is within this range, the PDO discharge efficiency is good and the melt-moldability is good.

In the PTT pellet of the present invention, the amount of the terminal carboxyl group of PTT is not more than 25 meq/kg, preferably 0 to 15 meq/kg. When the amount of the terminal carboxyl group is not more than 25 meq/kg, the resin composition will not be colored when heated and will have good oxidation resistance.

In the PTT pellet of the present invention, 0.01 to 2% by weight of bis (3-hydroxypropyl) ether (i.e., a dimer of PDO: hereinafter abbreviated as BPE) is copolymerized with PTT, preferably 0.05 to 1.5% by weight, more preferably 0.15 to 1.5% by weight, and still more preferably 0.3 to 1.5% by weight. The copolymerization of BPE tends to lower the light resistance and oxidation resistance stability of PTT, but if the copolymerization is carried out appropriately, the dye exhaustion rate and spinning stability are improved. However, if BPE is copolymerized in the above range, there is no problem in light resistance and oxidation resistance stability, dyeing properties are excellent, and crystallization does not excessively proceed in the solid phase polymerization stage in order to appropriately prevent crystallization, and breakage of pellets or powdering are suppressed.

The content of the cyclic dimer formed by dimerization of the trimethylene terephthalate units in the PTT pellet of the present invention is preferably not more than 1.5% by weight, more preferably not more than 1.2% by weight, further preferably not more than 0.7% by weight, most preferably 0% relative to the PTT. When the cyclic dimer content is not more than 1.5% by weight, no precipitation occurs during spinning or dyeing, and therefore, no yarn breakage or fuzz occurs, and no problems such as color spots occur. The cyclic dimer has the following chemical structure.

The crystallinity of the PTT pellet is preferably 40-60%, and more preferably 45-55%. If it is within this range, the pellets are not broken and no adhesion occurs between the pellets during solid-phase polymerization.

PTT pellets of the present invention, the dimensions thereofThe preferred hardness is 10-30 kg/mm²More preferably 15 to 28kg/mm². If it is within this range, the pellets are not broken and no adhesion occurs between the pellets during solid-phase polymerization.

In the PTT pellets of the present invention, the smaller the amount of the powdery material adhered to the pellets or mixed in the pellets, the better, it is preferably not more than 150ppm, more preferably not more than 50ppm relative to the pellets. The powder is fine powder passing through a 50 mesh sieve, and if the powder is excessive, a blower or an exhaust fan of an air conveyor (ニユ - マ - ライン) used for conveying pellets may be clogged to cause malfunction, or a screw pressure at the time of melt extrusion of pellets at the time of spinning or molding may be easily varied. The 50 mesh means that the mesh count is 50 at 1 inch (2.54cm) and the mesh size is about 300. mu.m.

The PTT pellets of the present invention are produced by solid-phase polymerization of pellets of a PTT prepolymer (hereinafter, simply referred to as prepolymer pellets) which satisfy the requirements described below. In this case, the prepolymer is a polymer before solid-phase polymerization, and has an intrinsic viscosity of at least 0.1dl/g lower than that of the polymer after solid-phase polymerization.

In the present invention, the inherent viscosity of the prepolymer pellets is 0.1 to 1dl/g, preferably 0.2 to 1dl/g, and more preferably 0.4 to 1 dl/g. If the intrinsic viscosity is within this range, it is possible to efficiently produce PTT pellets which are less broken pellets and less powdery substances are produced, have a terminal carboxyl group amount of not more than 25 meq/kg, have no viscosity difference between the inner and outer layers of the pellets, and are uniform and less colored by short-time solid-phase polymerization.

L of prepolymer pellets^*The value is not less than 75, preferably not less than 80. L is^*If it is not less than 75, L of PTT pellets obtained by solid-phase polymerizing the pellets^*The value was also high, and PTT pellets excellent in color tone were obtained. In addition, b^*The value is-3 to 6, preferably-1 to 5. b^*When the value is within this range, PTT pellets having an excessively strong cyan or yellow hue can be obtained.

In the invention, each prepolymer pellet is 1-50 mg/pellet, preferably 1-30 mg/pellet, and more preferably 1-25 mg/pellet. Within this range, PDO is appropriately discharged from the surface of the pellets in the solid phase polymerization stage, whereby pellets having excellent color tone and oxidation resistance stability are obtained, and since cracking of the pellets or generation of powder is small and partial adhesion of the pellets due to melting is also small, stable molding can be achieved when the pellets are subjected to a molding step.

From the viewpoint of suppressing the thermal decomposition at the time of solid-phase polymerization and suppressing the coloration of the PTT pellets after the solid-phase polymerization, the amount of the terminal carboxyl group of the prepolymer pellets is not more than 35 meq/kg, preferably 0 to 25 meq/kg. When the content is not more than 35 meq/mg, the coloring of the prepolymer pellets is small, so that the PTT pellets after solid-phase polymerization are hardly colored and the oxidation resistance stability is excellent.

The BPE copolymerized in the prepolymer pellets is 0.01 to 2 wt%. The preferable range and reason thereof are the same as those described above for the PTT pellets of the present invention.

Next, a method for producing the prepolymer pellets will be described.

The prepolymer pellets were made by the following three procedures: (1) an esterification reaction step of reacting terephthalic acid and/or a lower alcohol ester of terephthalic acid with PDO to produce bis (3-hydroxypropyl) terephthalate and/or an oligomer thereof (hereinafter abbreviated as BHPT), (2) a polycondensation step of heating the resultant reaction product to produce a prepolymer while distilling 1, 3-propanediol, and (3) a granulation step of granulating the prepolymer obtained by polycondensation.

First, the esterification reaction step (1) will be described.

The feeding molar ratio of PDO to terephthalic acid and/or a lower alcohol ester of terephthalic acid is preferably 0.8 to 3, more preferably 1.4 to 2.5, and still more preferably 1.5 to 2.3. When the feed ratio is within this range, the esterification reaction proceeds smoothly, and a polymer having a high degree of whiteness and a moderate melting point is obtained in the subsequent polycondensation step. In addition, it is preferable to use a lower alcohol ester of terephthalic acid as the raw material from the viewpoint of the good color tone of the obtained PTT pellets.

In order to make the reaction proceed smoothly, it is preferable to use a catalyst. Examples of the catalyst include titanium alkoxides typified by titanium tetrabutoxide and titanium tetraisopropoxide, amorphous titanium oxide precipitates, metal oxides such as amorphous titanium oxide/silica coprecipitates and amorphous zirconia precipitates, metal carboxylates such as calcium acetate, manganese acetate, cobalt acetate and antimony acetate, and germanium compounds such as germanium dioxide. The amount of the catalyst is preferably 0.01 to 0.2% by weight based on the total amount of the carboxylic acid component monomers, from the viewpoints of reaction rate and polymer whiteness.

The reaction temperature is about 200 to 250 ℃, and the reaction can be carried out while distilling off the by-product alcohol such as methanol. The reaction time is usually 2 to 10 hours, preferably 2 to 4 hours.

Next, the step of (2) polycondensation reaction will be described.

In the polycondensation reaction, if necessary, metal oxides such as titanium alkoxide represented by titanium tetrabutoxide and titanium tetraisopropoxide, amorphous titanium oxide precipitates, amorphous titanium oxide/silica coprecipitates, amorphous zirconium oxide precipitates, germanium compounds such as germanium dioxide, and the like may be further added in an amount of 0.01 to 0.2% by weight based on the total amount of the carboxylic acid component monomers, and the polycondensation reaction may be carried out by a known method. In order to obtain the objective prepolymer of the present invention, for example, the optimum polymerization time is selected so as to achieve 35 meq/kg while evaluating the amount of terminal carboxyl groups of the prepolymer at a polycondensation reaction temperature of preferably 240 to 270 ℃. The polymerization can be carried out usually within 4 hours, preferably within 1 to 3 hours, by the following vacuum degree and polymerization method. The polycondensation temperature is more preferably 250 to 265 ℃ and the degree of vacuum is preferably 0.0001 to 0.1 pKa.

In this case, the time from the normal pressure to the reduced pressure is important for appropriately adjusting the amount of BPE produced, and is preferably within 50 minutes to reduce the by-production of BPE. In addition, in order to suppress thermal decomposition and shorten the polycondensation reaction time, it is preferable to efficiently carry out the distillation removal of PDO during the polycondensation reaction. For this reason, it is important to increase the specific surface area of the polymer. For example, the reaction mixture is stirred ( き -stage) using a screw stirrer, a disk ring reactor or the like, and then efficiently stirred to form a thin film, and the feed ratio of the raw materials is preferably set to not more than 40% by volume, more preferably not more than 35% by volume, relative to the tank volume. Further, when the viscosity of the melt in the polycondensation reaction step increases with the lapse of time, the polycondensation reaction is preferably stopped. Even if the reaction time is prolonged, the melt viscosity does not increase any more and sometimes decreases, so it is important to terminate the polycondensation reaction before the decrease. The reason is that, when the melt viscosity is not increased any more but decreased in some cases even if the reaction time is prolonged, the thermal decomposition reaction is dominant over the polymerization reaction, and the amount of terminal carboxyl groups generated by thermal decomposition increases. In addition, the phosphorus compound, hindered phenol antioxidant, and color tone adjuster may be added at any stage of the polymerization reaction, preferably before the polymerization reaction.

Next, the granulation step is explained.

The method of taking out the polymer from the polymerizer and granulating the polymer includes, for example, taking out the polymer in the form of strands, pellets or the like in water, cooling the polymer, and cutting the polymer to obtain pellets of 1 to 50 mg/pellet. The cooling conditions are preferably cooling in cold water of not higher than 40 ℃ and more preferably not higher than 10 ℃ for 1 to 5000 seconds, and are preferable from the viewpoint of smoothness of cut surfaces. The shutdown may be performed during cooling or at any time after cooling is completed.

The pellet may be in the form of any of a rectangular parallelepiped, a cylinder, a dice, a ball, etc., but a cylinder is preferable from the viewpoint of easy handling and easy granulation. The size of the pellet is preferably 0.01 to 0.4cm in diameter and 0.1 to 0.6cm in length in terms of easy handling and difficulty in breaking during solid phase polymerization.

Next, the solid-phase polymerization step is explained.

The pellets of the prepolymer obtained above are subjected to solid phase polymerization to obtain the PTT pellets of the present invention. The solid-phase polymerizationis a method of heating the prepolymer pellets in a solid state to increase the intrinsic viscosity of the prepolymer pellets by at least 0.1dl/g or more as compared with the intrinsic viscosity of the prepolymer pellets.

Before the solid-phase polymerization, the pellets are preferably crystallized by heat treatment. By crystallization of the pellets, fluctuation in the extraction rate due to adhesion between pellets at the time of solid-phase polymerization can be suppressed. The heat treatment conditions are preferably in an inert gas atmosphere, the reachable temperature of the pellets is 190-225 ℃, and the time for maintaining the temperature is 5-120 minutes. Under such heat treatment conditions, the pellets can be prevented from adhering to the inner wall of the heat treatment apparatus, and the adhesion between the pellets in the solid phase polymerization apparatus can be effectively prevented, and further, crystallization can be sufficiently performed without spots, and breakage of the pellets or powdery substances are not generated.

In addition, in order to avoid the violent heat treatment and to prevent the occurrence of spots by crystallization through the heat treatment, a preliminary heat treatment may be performed at 80 to 180 ℃ for 5 to 120 minutes before the crystallization treatment. The crystallinity of the pellet thus obtained is preferably 20 to 60%, more preferably 40 to 50%.

The solid-phase polymerization is preferably carried out in an inert gas flow by appropriately controlling the temperature and the superficial velocity of the inert gas.

From the viewpoint of suppressing the coloration of the pellets and increasing the solid-phase polymerization rate, the temperature is preferably 190 to 220 ℃, more preferably 195 to 215 ℃, and most preferably 197 to 210 ℃. When the temperature is within this range, the solid-phase polymerization rate is appropriate, the pellets do not undergo discoloration or excessive crystallization during the solid-phase polymerization, and further, the fine powder does not adhere to the wall surface of the solid-phase polymerization vessel and becomes a high-polymerization-degree product or a high-crystallinity product without causing breakage of the pellets or generation of a powdery product, so that the melt stability during spinning or molding is good.

The atmosphere for carrying out the solid-phase polymerization may be a method carried out in an inert gas flow or a method carried out in a vacuum, and both of them are effective methods for efficiently discharging by-products such as water and PDO from the surface of the pellet.

First, the method carried out in an inert gas flow is explained.

The inert gas is a gas which does not substantially react with the PTT at the solid-phase polymerization temperature, and examples thereof include nitrogen, argon, and neon. Among them, nitrogen is preferably used in view of cost. If oxygen is contained in the inert gas, the oxygen content is preferably not higher than 100ppm relative to the inert gas because coloring is promoted by thermal decomposition at the time of solid-phase polymerization.

It is necessary to circulate the inert gas in the solid-phase polymerization vessel into which the pellets of the prepolymer are introduced, and the superficial velocity as the circulation amount of the inert gas at this time is not less than 10 cm/min from the viewpoint of the solid-phase polymerization rate. Further, the superficial velocity is the cross-sectional area (cm) of the solid-phase polymerization tank through which the gas passes²) By gas flow (cm)³Min) obtained. If the superficial velocity is not less than 10 cm/min, water produced from the pellets and by-products such as PDO can be dischargedfrom the pellet surface to the outside of the solid-phase polymerization vessel at a sufficient transfer rate, so that a sufficient solid-phase polymerization rate can be obtained and PTT pellets having a high polymerization degree can be obtained. The upper limit of the superficial velocity is not particularly limited, but the effect of discharging the polymerization by-product is not increased any more even if it exceeds 400 cm/min, so that it is set to be not higher than400 cm/min is economical. Further, if the superficial velocity of the inert gas is large, it is preferable from the viewpoint of moderating the friction between the pellets, suppressing the generation of cracks or dusts.

As a method of flowing the inert gas, for example, a method of continuously supplying pellets to one side of the solid-phase polymerization tank at a constant speed, flowing the inert gas in the reverse direction to the flow of the pellets, and continuously taking out the pellets from one side at the same speed as the supply speed of the pellets; and a method of introducing the pellets into a solid-phase polymerization vessel and preferably circulating an inert gas at a predetermined superficial velocity while stirring, the former method is preferable in order to suppress the generation of cracks or powder due to the friction between the pellets.

In the vacuum, the degree of vacuum is preferably not higher than 30kPa, more preferably not higher than 20kPa, most preferably 0.001 to 10kPa, for efficient discharge of the polymerization by-product.

The solid-phase polymerization vessel may be a reactor in which pellets are heated from the inner wall, for example, a silo-type reactor in which a pellet inlet is provided above a cylindrical tube and a bowl-shaped pellet outlet is provided below the cylindrical tube, and it is preferable that heat can be supplied from the outside by a heating medium, steam, or the like.

The feeding speed and the drawing speed of the pellets are preferably 50 to 1000 kg/hour, more preferably 100 to 400 kg/hour. The residence time of the beads in the solid phase polymerization apparatus is preferably 5 to 100 hours, more preferably 8 to 40 hours. Continuous solid-phase polymerization is more preferable because of higher productivity than batch-type methods in which solid-phase polymerization is carried out for each fixed amount.

After the solid-phase polymerization, the pellets are preferably cooled. The cooling of the pellets is important to stop the solid-phase polymerization reaction and to avoid the intrinsic viscosity of each pellet from being changed by preheating. The cooling conditions are not particularly limited as long as the pellets are cooled with water or the like under an inert atmosphere, and the temperature of the pellets is preferably set to not higher than 120 ℃ and more preferably not higher than 80 ℃.

In the present invention, a method of crystallizing pellets of a prepolymer by heat treatment, continuously feeding the pellets to a solid phase polymerization apparatus for solid phase polymerization, and then continuously taking out the pellets and cooling the pellets is preferred from the viewpoint of improving productivity. Further, the continuous solid-phase polymerization is more preferable in terms of production efficiency and stability because the supply rate and the withdrawal rate of the pellets are set to the same rate.

The PTT pellets of the present invention can be processed into a melt-molded article such as a fiber, a film or a molded article by a known method.

Best Mode for Carrying Out The Invention

The present invention will be further illustrated by the following examples, but the present invention is not limited to these examples.

The measurement method and the evaluation method are as follows.

(1) Intrinsic viscosity [ η]

The ratio (η sp/C) of the specific viscosity (η sp) to the concentration (C) (g/d1) in o-chlorophenol was extrapolated to a concentration of 0 using an Ostwald viscometer and determined by the following equation.

[η] = \lim_{C &RightArrow; O} (ηsp / C)

(2) Color tone (L)^*、b^*)

The cylindrical pellets of PTT were filled in a glass cuvette (inner diameter 61mm, depth 30mm) to 90 to 100% of the depth, and measured for CIE-L using a chromatism meter (SM-7-CH) manufactured by スガ (Japan K.K.) test^*a^*b^*(CIE1976) color series determination of L^*、b^*。

(3) Quality of pellet and production amount of powder

A predetermined amount of the pellets were washed with water on a 50-mesh sieve to remove powder having a size of 50 mesh or less adhering to the surfaces of the pellets.

Then, the pellets were dried in a hot air dryer, subjected to humidity control at 20 ℃ and a relative humidity of 65% for 24 hours, and the mass of 100 pellets was measured by electronic weighing under the humidity control, and the average mass of each pellet was determined as the mass of the pellets.

The powder passing through the 50-mesh sieve was dried and subjected to humidity conditioning under the same conditions, and the mass of the powder with respect to the mass of the pellets was determined as the amount of the powder produced.

(4) Amount of terminal carboxyl group

1g of PTT pellets were dissolved in 25ml of benzyl alcohol, 25ml of chloroform was added, and the titer (VA) (ml) of 1/50N potassium hydroxide in benzyl alcohol was determined. On the other hand, the titration amount was determined by blank titration without beads (V0). From these values, the amount of the terminal carboxyl group per gram of the pellet was determined by the following equation.

The amount of terminal carboxyl group (meq/kg) ═ VA-V0 × 20

(5) Copolymerization ratio of BPE

2g of micronized PTT pellets were weighed out accurately, and then charged into 25ml of a 2N methanolic potassium hydroxide solution, and solvolysis was carried out under reflux for 4 hours. The obtained decomposition product was used for quantification by gas chromatography.

The column was measured to 150 to 230 ℃ at a temperature rising rate of 20 ℃/min while flowing helium gas at a flow rate of 100 ml/min using DURABOND (registered trademark) DB-WAX (inner diameter: 0.25 mm. times. length: 30m (liquid film thickness: 0.25 μm)) manufactured by Agilent.

(6) Amount of cyclic dimer

0.3 g of a pellet was weighed, and the pellet was put into a mixture of 5ml of hexafluoropropanol and 5ml of chloroform and dissolved at room temperature. After completely dissolving, 5ml of chloroform was added, and 80ml of acetonitrile was further added. Then, the precipitated insoluble matter was filtered, and the entire filtrate was transferred to a 300ml flask, to which acetonitrile was added, to obtain a clear solution in a total amount of 200 ml. The solution was analyzed by high performance liquid chromatography and the amount of cyclic dimer was determined.

mu-Bondasphere (registered trademark) 15. mu.C-18-100A (3.9X 300mm) manufactured by Waters corporation was used for the column, and ultraviolet rays having a wavelength of 242nm were used for the detector. The measurement temperature was 45 ℃ and the mobile phase was 7/3 mixture of acetonitrile/water, and the flow rate was 1.5 ml/min.

(7) Superficial velocity of inert gas

Using cross-sectional area (cm) of solid phase polymerization apparatus through which inert gas flows²) Except the flow rate (cm) of the inert gas supplied to the solid phase polymerization apparatus in a standard state (0 ℃ C., 101kPa)³Min/min).

(8) Specific surface area of pellet

The surface area (S) (cm) of each pellet was measured by the BET adsorption method²Per), the specific surface area (S/W) of each pellet was calculated from the mass (W) (g/pellet) of the pellet. The surface area (S) was measured in a specific surface measuring apparatus using nitrogen gas and calculated by the following formula.

S＝σ×Vm×N

σ represents the area occupied by each nitrogen molecule of the adsorbed molecule on the surface of the bead, N represents the Avogardlo constant, and Vm represents the number of moles.

(9) Degree of crystallinity

10 beads were put into a direct-reading density gradient tube prepared using a light liquid (specific gravity: 1.240) and a heavy liquid (specific gravity: 1.590) prepared from a mixture of toluene and carbon tetrachloride. After 20 hours, the scale of the density gradient tube is read and the density d is calculated from a standard curve obtained from a curve with known density. Then, using this value, the crystallinity was determined by the following equation.

Crystallinity (%) { [ dc × (d-da)]/[ d × (dc-da)]} × 100

Wherein dc is the density of the complete crystal phase of 1.431 (g/cm)³) And da is the density of the amorphous phase 1.305 (g/cm)³)。

(10) Vickers hardness

According to JIS-Z-2244.

As far as possible, the test surface was a smooth surface for the pellet. In addition, when there was no smooth surface such as a spherical surface, a smooth surface cut with a sharp blade was used as a test surface.

The pellet was fixed to a jig so that the test indenter was vertically contacted, and protected for 15 seconds in a state where the indenter was pressed with a test pressure of 0.5 kgf.

The pressure was released, and the diagonal lengths (d1, d2) in 2 directions of the pits were measured while observing the surface with an optical microscope. Then, vickers hardness was obtained by the following equation.

Vickers hardness (kg/mm)²)＝0.9272/d²

Wherein d (mm) ═ d1+ d 2)/2.

(11) Compressive failure strength

According to JIS-K-7208 (compression failure strength).

In order to uniformly apply the compressive load, cylindrical pellets were used, and the upper and lower surfaces to which the load was applied were arranged in parallel. The pellets were clamped betweensmooth and mutually parallel compression clamps using an テンシロン compression tester (manufactured by オリエンテツク, UCT-10T) and applied with a load at a crosshead moving speed of 2 mm/min. The load (stress yield point) at the moment of fracture of the PTT pellets was determined, and the cross-sectional area to which the load was applied was divided to obtain a value as the compressive fracture strength.

(12) K/S value of woven fabric

The K/S value represents the surface coloring depth of the dye. The spectral reflectance (R) at the maximum absorption wavelength of the dyed knitted fabric was measured and determined by the Kubelka-Munk equation shown below. A larger value indicates a darker stain, i.e., better color development.

K/S＝(1-R)²/2R

Example 1

BHPT was produced by conducting an ester exchange reaction at 220 ℃ using 1300 parts by weight of dimethyl terephthalate, 1144 parts by weight of 1, 3-propanediol and 0.98 part by weight of titanium tetrabutoxide as an ester exchange catalyst. To the obtained BHPT, trimethyl phosphate was added in an amount of 20ppm in terms of phosphorus element relative to the obtained PTT, and then n-octadecyl 3- (3, 5 '-di-t-butyl-4' -hydroxyphenyl) propionate, which is a hindered phenol antioxidant, was added in an amount of 100ppm relative to the obtained PTT, and then titanium oxide, which is a delustering agent, was further added in an amount of 0.05 wt% relative to the obtained PTT, and the mixture was subjected to a polycondensation reaction at 260 ℃ and 0.07kPa for 3.5 hours under a reduced pressure for 20 minutes until the degree of vacuum (reduced pressure) became 0.07 kPa.

The polycondensate thus obtained was taken out through a circular take-out port having a bore diameter of 10mm into water atabout 5 ℃ and cut in water, centrifuged and dehydrated, and dried at 130 ℃ for 2 hours to give cylindrical pellets of the prepolymer.

The prepolymer pellets obtained had an intrinsic viscosity of 0.7dl/g, L^*Is 80, b^*1.3, the amount of the terminal carboxyl group was 21 meq/kg, the mass of the pellets was 25 mg/piece, the BPE copolymerization ratio was 0.13% by weight, the amount of the cyclic dimer was 2.7% by weight, and the specific surface area was 16cm²/g。

Then, the prepolymer pellets were charged into a solid phase polymerization apparatus, and crystallized by applying heat of 210 ℃ from the outer wall of the solid phase polymerization apparatus for 15 minutes while flowing at a superficial velocity of 100 cm/min (in terms of a standard state) with nitrogen gas heated to 205 ℃ as an inert gas. As a result, pellets having a crystallinity of 48% were obtained.

The pellets after crystallization were put into a solid phase polymerization apparatus, and solid phase polymerization was carried out for 30 minutes by heating the pellets to 205 ℃ with nitrogen gas flowing at a superficial velocity of 100 cm/min (in terms of standard state) and applying 205 ℃ heat from the outer wall. Then, cold water of 5 ℃ was introduced into the outer wall of the solid phase polymerization apparatus, and the pellets were cooled for 30 minutes under a nitrogen atmosphere to lower the temperature of the pellets to 60 ℃.

The pellets of PTT obtained by solid-phase polymerization had an intrinsic viscosity of 1.3dl/g, L^*Is 82, b^*3.0, the amount of the terminal carboxyl group was 13 meq/kg, the copolymerization ratio of BPE was 0.13% by weight,the cyclic dimer amount was 0.8 wt%. The contents of the phosphorus compound and the hindered phenol antioxidant in the pellets of PTT were the same as the amounts added during the polycondensation of PTT. The amount of the powder passing through a 50-mesh sieve produced in the crystallization and solid-phase polymerization was about 100ppm relative to the amount of the PTT pellets after the solid-phase polymerization.

To spin the PTT pellets, after drying 1g of the PTT pellets by flowing air heated to 140 ℃ at a flow rate of 0.1L/min for 3 hours, L was measured as the color tone of the pellets^*A value of 81, b^*At 3.2, the hue was hardly changed, indicating good oxidation resistance. The beads have a high degree of polymerization, a very high degree of whiteness, and little loss due to cracking in solid-phase polymerization. In addition, the compression failure strength of the pellets was 1200kg/cm²And is difficult to break.

The obtained PTT pellets were spun, knitted, formed and evaluated as described below.

The PTT pellets were dried in a nitrogen stream at 130 ℃ to a water content of 30 ppm. The pellets were fed into an extruder and extruded through a spinning die having a 36-hole circular discharge orifice with a pore diameter of 0.23mm at a temperature of 265 ℃. The screw pressure of the extruder was not varied, and smooth spinning was possible. The filaments discharged from the spinning nozzle were cooled and solidified by blowing cold air at a temperature of 20 ℃ and a relative humidity of 90% at a speed of 0.4 m/s. The solidified filaments were coated with a finishing agent and wound up at 1600 m/min to obtain undrawn filaments. Then, the obtained undrawn yarn was passed through a hot roll at 55 ℃ and a hot plate at 140 ℃ while being stretched until the degree of drawing reached about 40%, to obtain a drawn yarn of 50 dtex/36 f. The resulting whiteness is high, the strength is 4.2 cN/dtex, the modulus of elasticity is reduced to 25 cN/dtex, the feel is very soft and the stretchability is high.

A knitted fabric was produced using the obtained yarn, and a knitted fabric containing スコアロ - ル FC-250 (manufactured by Kao corporation, Note)Trademark), washed at 90 ℃ for 20 minutes, centrifugally dewatered, and then pre-set at 180 ℃ for 30 seconds using a pin tenter. Then, using 0.05% owf of dye Dianix Blue AC-E (ダイスタ - ジヤパン Co., Ltd., registered trademark), 1 g/liter of dispersant ニツカサンソルト 7000 (Niwaki chemical Co., Ltd., registered trademark), the pH of the dyeing bath was adjusted to be 1 g/liter with acetic acid and sodium acetate5.5, bath ratio 1: 50, dyeing at 120 ℃ for 30 minutes. The exhaustion of the dye was 98%. Then, dehydration is performed. The final setting was carried out at 170 ℃ for 30 seconds by a pin tenter to obtain a bright knitted fabric dyed in light cyan. K/S value of 0.7, b of the knit^*The value was-14.

In addition, pellets having a water content of 30ppm obtained by drying were put into an extruder and injection-molded in a mold at 245 ℃. The obtained molded article had good color tone and very high whiteness.

Example 2

PTT pellets were obtained in the same manner as in example 1 except that the solid-phase polymerization time was set to about 10 hours. The intrinsic viscosity of the obtained PTT pellets was 0.9dl/g, L^*Is 81, b^*2.2, the amount of the terminal carboxyl group was 15 meq/kg, the copolymerization ratio of BPE was 0.13% by weight, and the cyclic dimer was 1.0% by weight.

The amount of the powder passing through a 50-mesh sieve produced in the crystallization treatment and the solid-phase polymerization was about 50ppm relative to the amount of the PTT pellets, which were broken or pellets with a small degree of production of the powder. In addition, almost no coloration was observed in the same drying heat treatment at140 ℃ for 3 hours as in example 1.

Example 3

PTT pellets were obtained in the same manner as in example 1, except that the hindered phenol antioxidant was not added in the production process of the prepolymer pellets. The intrinsic viscosity of the obtained PTT pellets was 1.3dl/g, L^*Is 83, b^*3.2, the amount of terminal carboxyl groups was 15 meq/kg, the copolymerization ratio of BPE was 0.14 wt%, and the amount of cyclic dimer was 0.8 wt%.

In the crystallization treatment and solid phaseThe amount of the powder passing through the 50-mesh sieve produced in the polymerization was about 100ppm relative to the amount of the PTT pellets, which were broken or pellets producing little powder. Further, the color tone of the pellets after the drying heat treatment at 140 ℃ for 3 hours, L, was the same as that of example 1^*Is 82, b^*3.4, only slightly colored.

Example 4

In the production process of the PTT pellets of example 1, a series of steps of crystallizing, solid-phase polymerizing, and cooling the prepolymer pellets were performed while continuously supplying and discharging the pellets at a constant rate of 200 kg/hr. As a result, the time required for the series of steps was 33 hours in the batch treatment in example 1, while the time required for the continuous supply and discharge was 31 hours in this example, and the productivity was improved.

The obtained PTT pellets were excellent PTT pellets which were not inferior in quality to the pellets obtained in example 1, excellent in oxidation resistance stability, and less in the degree of cracking or generation of powdery substances.

Example 5

In the production process of the prepolymer pellets in example 1,the cutting conditions were changed to obtain pellets having a mass of 10 mg/pellet and a specific surface area of 22cm²Prepolymer pellets per gram. The pellets had almost no difference in intrinsic viscosity, hue, amount of terminal carboxyl group and copolycondensation ratio of BPE from example 1.

The prepolymer pellets were subjected to solid-phase polymerization under the same conditions as in example 1 for a short period of about 16 hours to give an intrinsic viscosity of 1.3dl/g, L^*Is 85, b^*2.1, the amount of the terminal carboxyl group was 12 meq/kg, the copolymerization ratio of BPE was 0.13% by weight, and the amount of the cyclic dimer was 0.7% by weight. The PTT pellets had higher whiteness and a smaller amount of terminal carboxyl groups than the pellets in example 1.

Since the solid-phase polymerization time is short, the amount of the powder passing through a 50-mesh sieve generated in the crystallization treatment and the solid-phase polymerization is very small, i.e., about 40ppm relative to the amount of the PTT pellets, and the PTT pellets are broken or the generation of the powder is low.In addition, although the amount of the terminal carboxyl group was somewhat smaller than that of the pellets of example 1, the color tone of the pellets was: l is^*Is 84, b^*2.2, only slightly colored.

Then, the above-mentioned PTT pellets were spun in the same manner as in example 1. The whiteness of the obtained silks is extremely high. Using the yarn, a knitted fabric was produced in the same manner as in example 1Dyeing and shaping. The resulting fabric was dyed a light cyan color, the K/S value of the fabric was 0.8, b^*The value was-20, and the sharpness of cyan was further improved as compared with that of example 1.

Further, injection molding was performed in the same manner as in example 1 to obtain a molded article. The resulting molded article had a further improved whiteness compared to the molded article of example 1.

Examples 6 and 7

In the prepolymer pellet production process of example 1, 43 mg/pellet and 15 mg/pellet of the prepolymer were obtained as shown in Table 1 by changing the cutting conditions. Then, solid-phase polymerization was carried out in about 40 hours and about 20 hours, respectively, in the same manner as in example 1. The obtained PTT pellets are excellent in whiteness and oxidation resistance stability, and are reduced in the degree of cracking or the generation of powdery substances.

Example 8

In the production process of the prepolymer pellets in example 1, the diameter of the hole of the take-out port of the polycondensation reactor was reduced, and the cutting conditions were changed to obtain 3 mg/pellet of the prepolymer. Then, solid-phase polymerization was carried out in about 10 hours as in example 1. The obtained PTT pellets are excellent in whiteness and oxidation resistance stability, and are reduced in the degree of cracking or the generation of powdery substances.

Example 9

In the production process of the prepolymer pellets in example 1, the polycondensation time was set to 2.5 hours, and after completion of the polycondensation, prepolymer pellets were obtained. Then, solid-phase polymerization was carried out in about 50 hours as in example 1. The obtained PTT pellets are excellent in whiteness and oxidation resistance stability, and are reduced in the degree of cracking or the generation of powdery substances.

Examples 10 and 11

PTT pellets were obtained in the same manner as in example 1 except that the nitrogen gas flow rate during the solid-phase polymerization was set to 350 cm/min and 20 cm/min, respectively, using an empty-column velocity meter. The obtained PTT pellets are excellent in whiteness and oxidation resistance stability, and are reduced in the degree of cracking or the generation of powdery substances.

Comparative example 1

In the production process of the prepolymer pellets in example 1, the inherent viscosity was 0.7dl/g and L was obtained by changing the cutting conditions^*Is 79, b^*1.8, the amount of terminal carboxyl groups was 23 meq/kg, the mass of the pellet was 60 mg/pellet, and the specific surface area was 10cm²(ii)/g, prepolymer pellets having a BPE copolymerization ratio of 0.3 wt% and a cyclic dimer content of 2.7 wt%.

When the obtained prepolymer pellets were subjected to solid-phase polymerization in the same manner as in example 1, about 60 hours were required to achieve a predetermined intrinsic viscosity. Since the solid-phase polymerization time is very long, the obtained PTT pellets have a low degree of whiteness, and the loss due to cracking in the solid-phase polymerization is very large. Further, the PTT pellets also had low compression fracture strength and oxidation resistance stability.

Then, using the obtained PTT pellets, spinning was performed in the same manner as in example 1, but the obtained filaments were slightly yellowish. A knitted fabric was produced using the yarn, dyed in the same manner as in example 1, and heat-set. The resulting fabric was dyed a light cyan color, the K/S value of the fabric was 0.6, b^*The value was-10, the yellow color was strong and had a dull, less vivid color tone than the knitted fabric of example 1.

Injection molding was performed in the same manner as in example 1 to obtain a molded article. The obtained molded article had a strong yellow color and a dull color compared with the molded article of example 1.

Comparative example 2

In the production process of the prepolymer pellets in example 1, polycondensation was carried out at 285 ℃ to obtain pellets having an inherent viscosity of 0.7dl/g and L^*Is 74, b^*7.0, the amount of terminal carboxyl group was 48 meq/kg, the mass of pellets was 25 mg/pellet, and the BPE copolymerization ratio was 0.70 weightAmount%, amount of cyclic dimer was 2.9% by weight of prepolymer pellets. The yellow color of the pellets was strong and the hue was dull.

Then, when solid-phase polymerization was carried out in the same manner as in example 1, the solid-phase polymerization time required about 70 hours. The obtained PTT pellets had a high content of terminal carboxyl groups, and thus were colored to a large extent, and were also colored to a large extent by the heat treatment for drying. Further, the obtained PTT pellets also had low oxidation resistance stability.

Comparative example 3

In the production process of the prepolymer pellets in example 1, polycondensation was carried out for 7 hours to obtain an intrinsic viscosity of 0.73dl/g, L^*Is 70, b^*8.3, the amount of terminal carboxyl groups was 52 meq/kg, the mass of pellets was 25 mg/piece, the copolymerization ratio of BPE was 0.75 wt%, and the amount of cyclic dimer was 2.9 wt%. The yellow color of the pellets was strong and the hue was dull.

Then, when solid-phase polymerization was carried out in the same manner as in example 1, the solid-phase polymerization time required about 90 hours. As shown in Table 1, the obtained PTT pellets had a high content of terminal carboxyl groups, and therefore were colored to a large extent, and were also colored to a large extent by the heattreatment for drying. Further, the obtained PTT pellets also had low oxidation resistance stability.

Comparative example 4

Solid-phase polymerization was carried out in the same manner as in example 1, except that the solid-phase polymerization temperature was set to 160 ℃ in the production process of the PTT pellets of example 1. However, even when the polymerization was carried out in a solid phase for about 60 hours, only an intrinsic viscosity of 0.72dl/g, L, was obtained^*Is 81, b^*The PTT pellets having a terminal carboxyl group content of 4.0, a BPE copolymerization ratio of 0.13 wt% and a cyclic dimer content of 2.0 wt% were unsatisfactory in terms of intrinsic viscosity and cyclic dimer content.

Comparative example 5

The solid-phase polymerization was carried out in the same manner as in example 1 except that the solid-phase polymerization temperature was set to 225 ℃ in the production process of the PTT pellets of example 1, thereby obtaining PTT pellets shown in Table 1. Although the solid-phase polymerization time is short, the obtained PTT pellets are also very colored, and the pellets are also very colored by the drying heat treatment. In addition, the pellets have low compressive failure strength and low oxidation resistance stability.

Comparative example 6

Except that in the production process of PTT pellets of example 1, nitrogen gas in the solid-phase polymerization was usedThe solid-phase polymerization was carried out in the same manner as in example 1 except that the flow rate was set to 1 cm/min using an empty-column velocity meter, to obtain PTT pellets as shown in Table 1. The transfer of PDO to the outside of the solid phase polymerization vessel was insufficient, and the polymerization was difficult, and only the intrinsic viscosity of0.75dl/g, L was obtained even when the solid phase polymerization was carried out for about 60 hours^*Is 71, b^*6.5, the amount of the terminal carboxyl group was 26 meq/kg, the copolymerization ratio of BPE was 0.25% by weight, the amount of the cyclic dimer was 1.8% by weight, and the color of the resulting PTT beads was large. In addition, the pellets have low compressive failure strength and low oxidation resistance stability.

Comparative example 7

In the production process of the prepolymer pellets in example 1, the diameter of the hole of the take-out port of the polycondensation vessel was reduced and the cutting conditions were changed to obtain pellets of 0.6 mg/pellet, but cutting was not smoothly performed, and instead, pellets having very large fluctuation in the mass per pellet were obtained.

Comparative example 8

BHPT was produced by conducting an esterification reaction at 250 ℃ using 1100 parts by weight of terephthalic acid, 1700 parts by weight of 1, 3-propanediol, and 0.98 part by weight of titanium tetrabutoxide as a transesterification catalyst. To the obtained BHPT, trimethyl phosphate was added in an amount of 20ppm in terms of phosphorus element based on the obtained PTT, and then n-octadecyl 3- (3, 5 '-di-t-butyl-4' -hydroxyphenyl) propionate, which is a hindered phenol antioxidant, was added in an amount of 100ppm based on the obtained PTT, and the mixture was subjected to a polycondensation reaction under a vacuum condition of 0.07kPa for 1 hour at 260 ℃ for 3.5 hours to obtain a polycondensate. Then, the diameter of the take-out port of the polycondensation vessel was set to 10mm, the polycondensate was taken out into water at about 5 ℃ and cut in water, centrifuged, and dried at 130 ℃ for 2 hours to obtain cylindrical pellets of the prepolymer.

The solid state of the prepolymer pellets obtainedHas a viscosity of 0.7dl/g, L^*Is 81, b^*6.3, the amount of the terminal carboxyl group was 38 meq/kg, the mass of the pellets was 25 mg/piece, the BPE copolymerization ratio was 2.12% by weight, the amount of the cyclic dimer was 2.7% by weight, and the specific surface area was 16cm²/g。

The prepolymer pellets were subjected to solid-phase polymerization in the same manner as in example 1 to obtain PTT pellets. The obtained PTT pellets have poor whiteness and oxidation resistance stability.

In the above examples and comparative examples, the characteristic values of the prepolymer pellets are shown in Table 1, and the solid-phase polymerization conditions and the characteristic values of the PTT pellets are shown in Table 2.

TABLE 1

	Prepolymer pellets
	Prepolymer pellets						[η] (dl/g)	Color tone L^/b^	Quality of (mg/one)	Terminal COOH (milliequivalent/kg)	BPE is altogetherPoly ratio (wt%)	Cyclic D amount (wt%)
	Example 1	0.7	80/1.3	25	21	0.13	[η] (dl/g)	Color tone L^/b^	Quality of (mg/one)	Terminal COOH (milliequivalent/kg)	BPE is altogetherPoly ratio (wt%)	Cyclic D amount (wt%)	2.7
Example 2	Example 1	0.7	80/1.3	25	21	0.13	0.7	80/1.3	25	21	0.13	2.7	2.7
Example 2	Example 3	0.7	81/1.5	25	24	0.14	0.7	80/1.3	25	21	0.13	2.7	2.8
Example 4	Example 3	0.7	81/1.5	25	24	0.14	0.7	80/1.3	25	21	0.13	2.7	2.8
Example 4	Example 5	0.7	81/1.4	10	21	0.13	0.7	80/1.3	25	21	0.13	2.7	2.7
Example 6	Example 5	0.7	81/1.4	10	21	0.13	0.7	80/2.0	43	22	0.13	2.7	2.7
Example 6	Example 7	0.7	80/1.5	15	21	0.13	0.7	80/2.0	43	22	0.13	2.7	2.7
Example 8	Example 7	0.7	80/1.5	15	21	0.13	0.7	83/2.2	3	21	0.13	2.7	2.7
Example 8	Example 9	0.6	85/-1	25	12	0.10	0.7	83/2.2	3	21	0.13	2.7	2.3
Example 10	Example 9	0.6	85/-1	25	12	0.10	0.7	80/1.3	25	21	0.13	2.7	2.3
Example 10	Example 11	0.7	80/1.3	25	21	0.13	0.7	80/1.3	25	21	0.13	2.7	2.7
Comparative example 1	Example 11	0.7	80/1.3	25	21	0.13	0.7	79/1.8	60	23	0.13	2.7	2.7
Comparative example 1	Comparative example 2	0.7	74/7.0	25	48	0.70	0.7	79/1.8	60	23	0.13	2.7	2.9
Comparative example 3	Comparative example 2	0.7	74/7.0	25	48	0.70	0.73	70/8.3	25	52	0.75	2.9	2.9
Comparative example 3	Comparative example 4	0.7	80/1.3	25	21	0.13	0.73	70/8.3	25	52	0.75	2.9	2.7
Comparative example 5	Comparative example 4	0.7	80/1.3	25	21	0.13	0.7	80/1.3	25	21	0.13	2.7	2.7
Comparative example 5	Comparative example 6	0.7	80/1.3	25	21	0.13	0.7	80/1.3	25	21	0.13	2.7	2.7
Comparative example 8	Comparative example 6	0.7	80/1.3	25	21	0.13	0.7	81/6.3	25	38	2.13	2.7	2.7

Note: terminal COOH: amount of terminal carboxyl group

Amount of cyclic D: trimethylene terephthalate cyclic dimer content

TABLE 2

	Conditions of solid phase polymerization			PTT pellet
	Conditions of solid phase polymerization			PTT pellet												Temperature of (℃ )	Empty tower Speed of rotation (cm/min)	Time of day (hours)	[η] (dl/g)	Color tone L^/b^	Quality of (mg/one)	End tip COOH (milliequivalent/kg)	BPE Copolymerization ratio (wt%)	In the form of a ring Amount of D (wt%)	Proportion table Area of (cm²/g)	Crystallization of Degree of rotation (％)	Powder form Volume measurement (ppm)	Compressed crusher Bad strength (kg/cm²)	After drying Color tone of (2) L^/b^	Vickers hardness (kg/mm²)
	Example 1	205	100	30	1.3	82/3.0	25	13	0.13	0.8	16	49	100	1200	81/3.2	Temperature of (℃ )	Empty tower Speed of rotation (cm/min)	Time of day (hours)	[η] (dl/g)	Color tone L^/b^	Quality of (mg/one)	End tip COOH (milliequivalent/kg)	BPE Copolymerization ratio (wt%)	In the form of a ring Amount of D (wt%)	Proportion table Area of (cm²/g)	Crystallization of Degree of rotation (％)	Powder form Volume measurement (ppm)	Compressed crusher Bad strength (kg/cm²)	After drying Color tone of (2) L^/b^	Vickers hardness (kg/mm²)	22
Example 2	Example 1	205	100	30	1.3	82/3.0	25	13	0.13	0.8	16	49	100	1200	81/3.2	205	100	10	0.9	81/2.2	25	15	0.13	1.0	16	47	50	1300	80/3.0	21	22
Example 2	Example 3	205	100	30	1.3	83/3.2	25	15	0.14	0.8	16	49	100	1220	82/3.4	205	100	10	0.9	81/2.2	25	15	0.13	1.0	16	47	50	1300	80/3.0	21	22
Example 4	Example 3	205	100	30	1.3	83/3.2	25	15	0.14	0.8	16	49	100	1220	82/3.4	205	100	30	1.3	82/2.8	25	13	0.13	0.8	16	49	80	1200	81/3.1	22	22
Example 4	Example 5	205	100	16	1.3	85/2.1	10	12	0.13	0.7	22	49	40	1250	84/2.2	205	100	30	1.3	82/2.8	25	13	0.13	0.8	16	49	80	1200	81/3.1	22	21
Example 6	Example 5	205	100	16	1.3	85/2.1	10	12	0.13	0.7	22	49	40	1250	84/2.2	205	100	40	1.3	78/4.2	43	23	0.13	0.8	12	50	500	1000	77/5.0	23	21
Example 6	Example 7	205	100	20	1.3	84/2.3	15	13	0.13	0.8	20	48	55	1400	83/2.2	205	100	40	1.3	78/4.2	43	23	0.13	0.8	12	50	500	1000	77/5.0	23	22
Example 8	Example 7	205	100	20	1.3	84/2.3	15	13	0.13	0.8	20	48	55	1400	83/2.2	205	100	10	1.3	85/2.4	2	17	0.13	0.9	28	47	300	1450	84/2.2	22	22
Example 8	Example 9	205	100	50	1.3	86/1.2	24	9	0.10	0.7	17	56	300	1000	85/1.5	205	100	10	1.3	85/2.4	2	17	0.13	0.9	28	47	300	1450	84/2.2	22	24
Example 10	Example 9	205	100	50	1.3	86/1.2	24	9	0.10	0.7	17	56	300	1000	85/1.5	205	350	28	1.3	83/2.7	25	12	0.13	0.8	16	48	100	1250	81/3.2	22	24
Example 10	Example 11	205	20	40	1.3	80/3.2	24	12	0.13	0.8	17	50	300	1100	79/3.0	205	350	28	1.3	83/2.7	25	12	0.13	0.8	16	48	100	1250	81/3.2	22	23
Comparative example 1	Example 11	205	20	40	1.3	80/3.2	24	12	0.13	0.8	17	50	300	1100	79/3.0	205	100	60	1.3	73/7.2	58	26	0.14	0.9	10	51	2000	800	72/9.0	26	23
Comparative example 1	Comparative example 2	205	100	70	1.3	71/9.5	24	27	0.71	1.2	16	49	1200	1200	67/11.0	205	100	60	1.3	73/7.2	58	26	0.14	0.9	10	51	2000	800	72/9.0	26	25
Comparative example 3	Comparative example 2	205	100	70	1.3	71/9.5	24	27	0.71	1.2	16	49	1200	1200	67/11.0	205	100	90	1.3	73/11.5	23	32	0.77	1.3	16	48	1500	1100	70/13.2	31	25
Comparative example 3	Comparative example 4	160	100	60	0.72	81/4.0	24	18	0.13	2.0	16	47	1000	1200	80/4.5	205	100	90	1.3	73/11.5	23	32	0.77	1.3	16	48	1500	1100	70/13.2	31	20
Comparative example 5	Comparative example 4	160	100	60	0.72	81/4.0	24	18	0.13	2.0	16	47	1000	1200	80/4.5	225	100	23	1.3	70/10.8	25	27	0.18	1.6	16	53	90	800	68/12.5	28	20
Comparative example 5	Comparative example 6	205	1	60	0.75	71/6.5	24	26	0.25	1.8	16	52	1300	800	69/8.2	225	100	23	1.3	70/10.8	25	27	0.18	1.6	16	53	90	800	68/12.5	28	20
Comparative example 8	Comparative example 6	205	1	60	0.75	71/6.5	24	26	0.25	1.8	16	52	1300	800	69/8.2	205	100	30	1.26	81/5.2	25	28	2.14	1.2	16	48	700	1300	69/9.6	21	20

Note: terminal COOH: amount of terminal carboxyl group

Amount of cyclic D: trimethylene terephthalate cyclic dimer content

Industrial applicability

The PTT pellets of the present invention have a high polymerization degree, a good color tone, and a much smaller degree of breakage or generation of powder than in the conventional cases, and have excellent melt-moldability, and therefore, can be suitably used in a wide range of applications such as fibers, films, and molded articles.

Claims

1. A polytrimethylene terephthalate pellet which satisfies the following (1) to (7):

(1) the poly (trimethylene terephthalate) is a poly (trimethylene terephthalate) wherein not less than 80% by weight of the repeating units are made up of trimethylene terephthalate units,

(2) the polytrimethylene terephthalate is copolymerized with bis (3-hydroxypropyl) ether in a copolymerization ratio of 0.01 to 2% by weight,

(3) the amount of terminal carboxyl groups of the polytrimethylene terephthalate is not more than 25 meq/kg,

(4) the intrinsic viscosity of the polytrimethylene terephthalate is 0.8 to 2dl/g,

(6) b of the pellet^*The amount of the organic solvent is-2 to 5,

(7) the mass of each small ball is 1-50 mg/piece.

2. The poly (trimethylene terephthalate) pellet of claim 1, wherein the trimethylene terephthalate cyclic dimer content is not greater than 1.5 wt%.

3. The polytrimethylene terephthalate pellets as claimed in claim 1 or 2, wherein the specific surface area of each pellet is 10 to 50cm²/g。

4. The poly (trimethylene terephthalate) pellet as claimed in claim 1, wherein the crystallinity is 40-60%.

5. The polytrimethylene terephthalate pellets as claimed in claim 1, wherein the Vickers hardness is 10 to 30kg/mm²。

6. A process for producing pellets of polytrimethylene terephthalate, characterized by solid-phase polymerizing pellets of a prepolymer of polytrimethylene terephthalate satisfying the following (1) to (7):

(3) the amount of terminal carboxyl groups of the polytrimethylene terephthalate is not more than 35 meq/kg,

(4) the polytrimethylene terephthalate has an intrinsic viscosity of 0.1 to 1dl/g,

(6) b of prepolymer pellets^*The amount of the organic acid is-3 to 6,

(7) the mass of each prepolymer pellet is 1-50 mg/pellet.

7. The process for producing polytrimethylene terephthalate pellets according to claim 6, wherein the solid-phase polymerization is carried out in an inert gas stream under the following conditions (1) and (2),

(1) the solid-phase polymerization temperature is 190-220 ℃,

(2) the superficial velocity of the inert gas is not less than 10 cm/min.

8. The process for producing polytrimethylene terephthalate pellets as claimed in claim 6, wherein the solid-phase polymerization is carried out under reduced pressure under the following conditions (1) and (2),

(1) the solid-phase polymerization temperature is 190-220 ℃,

(2) the degree of vacuum was not higher than 30 kPa.

9. The process for producing polytrimethylene terephthalate pellets according to any one of claims 6 to 8, wherein the solid-phase polymerization is carried out after the heat treatment is carried out in advance to make the crystallinity 20 to 60% before the solid-phase polymerization.

10. The method for producing the polytrimethylene terephthalate pellets as claimed in any one of claims 6 to 9, wherein the solid-phase polymerization is continuous solid-phase polymerization or batch solid-phase polymerization.

11. A melt-molded article using the polytrimethylene terephthalate pellet as claimed in any one of claims 1 to 5.